Project 1 ? Summary: Adoptive T cell therapy (ACT) has demonstrated dramatic therapeutic benefit in hematologic cancers. However, the identification and generation of cancer-specific T cells is laborious, the expansion rates and functionality of these T cell products are limited, and on-target and off-target side effects can carry substantial morbidity. New biomaterials can potentially overcome many current challenges related to T cell-mediated cancer immunotherapy. We recently developed a 3D system that mimics antigen-presenting cells (APCs). These biodegradable, APC-mimetic scaffolds (APC-ms) consist of a fluid lipid bilayer supported by mesoporous silica micro-rods (MSRs), enabling precise spatial and temporal presentation of membrane-bound and soluble cues for T cell activation. APC-ms enable robust antigen-specific expansion of rare cytotoxic T-cell subpopulations at a greater magnitude than autologous monocyte-derived dendritic cells, and in a xenograft lymphoma model, CD19 CAR- T cells expanded using APC-ms improved anti-tumor efficacy and overall survival, as compared to Dynabead-expanded cells. Importantly this ?mix and match? APC-ms technology, makes it possible to simply combine various stimulatory, co-stimulatory and cytokine cues, and incorporate each in pre-defined compositions to enable unprecedented precision and accuracy in mimicking and modulating how APCs naturally signal to T cells. APC-ms can be configured to expand T cells of defined multi-epitope specificity, which would be expected to provide greater anti-tumor activity than cellular products of a single specificity, potentially limiting immune-escape mechanisms. We propose to develop this approach for both solid tumors and hematologic malignancies with the following aims: (1) Define optimal conditions for expanding rare tumor- specific human CD8 T cells while preserving high functionality. We will optimize the APC-ms system for human T cells specific for defined melanoma antigen MART1 to best support expansion of stem and central memory MART1-specific T cells. We will test if the expanded cells provide control of tumor growth in vivo in xenograft models of HLA-A2+ MART1+ melanoma, (2) Adapt the APC-ms system for generating polyclonal CD8 T cells expanded against multiple epitopes. Experiments will utilize PBMC collected from 2 melanoma patients vaccinated against up to 20 personal neoantigens, and already known to have rare but detectable populations of neoantigen-specific CD8 T cells. Studies will determine if APC-ms can preferentially expand rare CD8 T cells that are cytotoxic against autologous melanoma, (3) Utilize APC-ms to expand hematopoietically-restricted minor histocompatibility antigen (mHAg)-specific T cells from patients with AML. We will use WES-based discovery of tumor mutations and private SNPs from recipients of whole AML cell vaccines to predict candidate tumor antigens from 5 subjects. Experiments will test the ability of APC-ms to expand polyclonal hematopoietic mHAg- specific T cells and the ability of these cells to exert tumor control in AML primagraft models.